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SFTP IdentityFile

In the realm of secure file transfers, the Secure File Transfer Protocol (SFTP) stands out as a preferred method. SFTP, a component of the Secure SHell (SSH) protocol, offers a mechanism to securely transfer files between local and remote systems. One of its features, the IdentityFile option, allows users to authenticate using private and public key pairs rather than relying solely on passwords. In this article, we'll explore how to use the IdentityFile option with SFTP for enhanced security.

What is IdentityFile?

The IdentityFile option points to a private key file used for public key authentication. In simpler terms, instead of using a password, a user can present a private key to prove their identity to the server. The server then verifies this by checking against the corresponding public key it has stored. This method of authentication is not only secure but also facilitates automating processes without the need for manual password entry.

How to Use IdentityFile with SFTP

To initiate an SFTP connection using a private key, the -i flag followed by the path to the private key is used. The general format is:
sftp -i /path/to/your/private_key_file username@remote_server_address
  • /path/to/your/private_key_file is the location of your private key on the local machine.
  • username is the username on the remote server.
  • remote_server_address is the address or IP of the remote server.
  • For security purposes, the private key file should have restrictive permissions to prevent unauthorized access. It's widely recommended to set the permissions to 600 :
    chmod 600 /path/to/your/private_key_file
    This ensures that only the file's owner can read and write to it, keeping it protected from other users.

    Configuring the Remote Server

    For the server to recognize and trust the private key, the corresponding public key must be added to the ~/.ssh/authorized_keys file on the server. If the remote server's SSH/SFTP service isn't running on the default port (22), the connection can be adjusted using the -oPort option:
    sftp -i /path/to/your/private_key_file -oPort=2222 username@remote_server_address


    Using the IdentityFile option with SFTP provides a secure alternative to password-based authentication. When implemented correctly, it can enhance the security of file transfers while also offering convenience for automated workflows. As always, it's essential to keep private keys confidential and protected. If there's ever a suspicion of compromise, generating a new key pair should be the immediate course of action.